A251240 Indices of squares of primes in A098550.

4, 5, 11, 40, 124, 187, 273, 313, 505, 747, 751, 1280, 1478, 1563, 1841, 2386, 3130, 3134, 4196, 4493, 4497, 5455, 6002, 6877, 8158, 9047, 9276, 10190, 10194, 11157, 14182, 15086, 16762, 16766, 19758, 20051, 21749, 23435, 24601, 26398, 28655, 28659, 32636

Offset: 1

Author

Reinhard Zumkeller, Dec 02 2014

Keywords

• nonn

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..175

Crossrefs

Subsequence of A251241.

Cf. A001248, A062799, A098550.

Programs

Haskell

a251240 n = a251240_list !! (n-1)
a251240_list = filter ((== 2) . a062799 . fromIntegral . a098550) [1..]

Python

from gmpy2 import gcd, is_square, is_prime, isqrt
A251240_list, l1, l2, s, b = [], 3, 2, 4, {}
for n in range(4,10**4):
    i = s
    while True:
        if not i in b and gcd(i,l1) == 1 and gcd(i,l2) > 1:
            l2, l1, b[i] = l1, i, 1
            while s in b:
                b.pop(s)
                s += 1
            if is_square(i) and is_prime(isqrt(i)):
                A251240_list.append(n)
            break
        i += 1
print(A251240_list) # Chai Wah Wu, Dec 06 2014

Formula

A098550(a(n)) = A001248(n).

A062799(A098550(a(n))) = 2.